Kick things off by tossing your sliced mushrooms and diced onions into the bottom of your trusty slow cooker. They'll create a flavorful bed for our steaks.

Now, let's get our hands dirty! Mix up all the beef patty ingredients in a bowl. Once everything's well combined, shape the mixture into 6 patties. Don't worry if they're not perfect – they'll still taste great!

Time to give those patties some color. Heat up a skillet over medium-high heat and sear each patty for about 3 minutes per side. This step adds a ton of flavor and helps the patties keep their shape.

Carefully transfer your browned patties to the slow cooker, layering them over the mushrooms and onions.

In a separate bowl, whisk together all the gravy ingredients except the water and cornstarch. This is where the magic happens – pour this savory mixture over your beef patties.

Pop the lid on your slow cooker and let it work its magic on low for 5 to 6 hours. Your kitchen's going to smell amazing!

Once the time's up, gently remove the patties and set them aside. Don't worry, we're not done yet!

For the finishing touch, mix cold water and cornstarch in a small bowl until smooth. Stir this slurry into the hot gravy in the slow cooker. Let it bubble away for a few minutes until it thickens up nicely.

Finally, nestle those tender patties back into the gravy, and you're ready to serve! Spoon this comfort food goodness over a pile of creamy mashed potatoes or fluffy rice.